This work aimed to describe a mechanistic model for soil heterotrophic respiration, to apply it to an agricultural soil and to specify its important parameters, in order to define future research fields ... [more ▼]

This work aimed to describe a mechanistic model for soil heterotrophic respiration, to apply it to an agricultural soil and to specify its important parameters, in order to define future research fields. A complete description of the model structure is given. It uses a daily time step and is derived from the CENTURY model. The model was found to be independent from the initial carbon pool contents and an exponential relationship was observed between the order of stabilisation of the different pools and their respective decomposition constants. Literature was scanned to provide a panel of biochemical parameter values (nitrogen, lignin, cellulose and hemicellulose contents) for wheat, sugar beet and potato crops. Large parameter ranges of values were noticed and a lack of information about sugar beet and potato crops drove our choice to work with wheat biochemical parameters later on. An exponential relationship between two parameters linked to the effect of temperature on microbial respiratory activity, respectively Tb and h, was highlighted. For a fixed value of Q10, the values of these two parameters varied in opposite ways. The sensitivity analysis was performed at both short and long terms, mainly on the basis of carbon pool contents. The results were very variable from one pool to another. In both analyses Tb and h appeared to be the most sensitive parameters while some differences between both time spans were noticed, notably because of pool stabilisation dynamics and crop residue types. In the end, the combination of sensitivity values with parameter ranges of values brought us to consider the parameters Tb, h, Nlit (% nitrogen in above-ground residues) and Lignlit (% lignin in above-ground residues) and the forcing variables MBR (root residues quantity) and Litfall (above-ground residues quantity) as the features about which further investigations would be needed. The integration of this mechanistic model into a more complete one, also taking account of autotrophic respiration and CO2 diffusion in soils, is a further goal to achieve. [less ▲]

Currently, the art criticism encounters changes that come from the transformation of its objects and of its broadcast mediums in the digital age. To understand these changes and to evaluate the issues, we ... [more ▼]

Currently, the art criticism encounters changes that come from the transformation of its objects and of its broadcast mediums in the digital age. To understand these changes and to evaluate the issues, we will examine the art criticism through the lense of olfactory art to show how this very specific art brings out the subjectivity, the perceptual habitus as well as the scientific and industrial limits of the art criticism. [less ▲]

Ammonia is used in the industry for the manufacture of fertilizers, explosives and polymers and is stored at -33°C in refrigerated tanks. In most cases, tanks are cylindrical and are composed of a steel ... [more ▼]

Ammonia is used in the industry for the manufacture of fertilizers, explosives and polymers and is stored at -33°C in refrigerated tanks. In most cases, tanks are cylindrical and are composed of a steel liner that contains the ammonia, with the liner itself being protected by an outer reinforced concrete tank. The function of the concrete tank is to keep the ammonia safe in case of a leak in the liner. If a leak happens, the concrete wall will be suddenly subjected to a thermal shock, with a large temperature gradient between its internal and external faces (20°C to -33°C). These thermal effects lead to cracks in concrete that allow the ammonia to escape. The junctions between walls and the base slab and, walls and the roof are particularly sensitive to this cracking phenomenon. The aim of this paper is to present a method for the design of concrete ammonia tanks, especially taking into account thermal effects. Firstly, a 2D finite element model based on a plane frame is developed. The advantage of this approach, compared to 3D modelling, is that it requires little computing power and engineering time. Then, a 3D model is used to validate the 2D approach, and to identify its limitations. Particular attention is paid to the modeling of the weakest parts of the structure. Lastly, the paper will give the results of a parametric study based on the above 2D and 3D finite element modelling, in order to establish general guidelines for the design of ammonia tanks. [less ▲]

Participation to a workshop on specific issues in ethnography: how to describe accurately and efficiently the objects present on the fieldwork? Each participant brings a short text with a depiction of a ... [more ▼]

Participation to a workshop on specific issues in ethnography: how to describe accurately and efficiently the objects present on the fieldwork? Each participant brings a short text with a depiction of a particular object (tool, organization, vehicle, apparatus, document, etc.), and try to show how it feeds the thin understanding of the situation, and allows a certain theoretical analysis. All participants comment the other texts and propose solutions to improve the quality of texts [less ▲]

Automated resource exchange and negotiation between participants of a Virtual Organization, or Peers of a Peer-to-Peer Grid, is an important feature of Grid computing because it enables scalable ... [more ▼]

Automated resource exchange and negotiation between participants of a Virtual Organization, or Peers of a Peer-to-Peer Grid, is an important feature of Grid computing because it enables scalable cooperation between entities under separate administrative control. Automated negotiation and accounting of resource consumption have been studied, and market-based resource exchange methods have been proposed. However, there currently exist few simulators of resource exchange accounting or actual Grid middlewares supporting negotiation with automated resource usage accounting between separate entities. We propose a Lightweight Bartering Grid (LBG) architecture suitable to the development of Peer-to-Peer Grids based on bartering (i.e. automated and accounted resource exchange), where Peers model their environment. We present the LBG architecture as well as a simulator and a middleware under development that both instantiate it. [less ▲]

Nowadays, in newly built housings, energy losses due to the ventilation can represent up to 50 % of the total building energy consumption. As a result, heat recovery ventilation units are widely used in ... [more ▼]

Nowadays, in newly built housings, energy losses due to the ventilation can represent up to 50 % of the total building energy consumption. As a result, heat recovery ventilation units are widely used in order to save primary energy and different control strategies for ventilation systems are investigated. For instance, demand control ventilation sounds like a promising solution to decrease the energy impact of the ventilation system in the residential sector. An accurate building model integrating the influence of ventilation (so called thermo-aeraulic building model) is necessary in order to investigate the control and the impact of the ventilation system on a yearly basis. The aim of the present paper consists in a description of a combined multi-zone airflow network model and thermal building model implemented in the Modelica language. The thermal model is a simplified dynamic model using equivalent thermal resistance and capacity. The airflow network is based on the traditional electrical circuit analogy. The model can be used for ventilation systems design, infiltration rate calculation, inside air quality calculation, energy consumption calculation, etc. The first part of the paper details the multi-zone thermal building model. The results obtained from the model are compared to experimental in situ results collected in the typical single family house test facilities. Those experimental results have been obtained in the frame of the IEA-EBC Annex 58. The second part of the paper introduces the multi-zone airflow network building model. Obtained model results are compared with the results provided by a typical multizone airflow analysis software, for a simple three zones test case. The third part of the paper describes the coupling between both thermal and airflow models. The different numerical problems encountered are described and solutions are discussed. [less ▲]

Forest ecosystems play a major role in atmospheric carbon sequestration and emission. Comparable organic carbon stock estimates at temporal and spatial scales for all forest pools are needed for ... [more ▼]

Forest ecosystems play a major role in atmospheric carbon sequestration and emission. Comparable organic carbon stock estimates at temporal and spatial scales for all forest pools are needed for scientific investigations and political purposes. Therefore, we developed a new carbon stock (CS) estimation procedure that combines forest inventory and soil and litter geodatabases at a regional scale (southern Belgium). This procedure can be implemented in other regions and countries on condition that available external carbon soil and litter data can be linked to forest inventory plots. The presented procedure includes a specific CS estimation method for each of the following forest pools and subpools (in brackets): living biomass (aboveground and belowground), deadwood (dead trees and snags, coarse woody debris and stumps), litter, and soil. The total CS of the forest was estimated at 86 Tg (185 Mg ha-1). Soil up to 0.2 m depth, living biomass, litter, and deadwood CSs account, respectively, for 48, 47, 4, and 1 % of the total CS. The analysis of the CS variation within the pools across ecoregions and forest types revealed in particular that: (1) the living biomass CS of broadleaved forests exceeds that of coniferous forests, (2) the soil and litter CSs of coniferous forest exceed those of broadleaved forests, and (3) beech stands come at the top in carbon stocking capacity. Because our estimates differ sometimes significantly from the previous studies, we compared different methods and their impacts on the estimates. We demonstrated that estimates may vary highly, from -16 to ?12 %, depending on the selected methods. Methodological choices are thus essential especially for estimating CO2 fluxes by the stock change approach. The sources of error and the accuracy of the estimates were discussed extensively. [less ▲]